every pc has an ip adress the ones in a cafe at work in a library and they are not registered to anyone in particular neither is your pc probably.
only a small amount of very clever nutjobloopyloos would be able to find an ip adress, you have to have special data tracking kit and it would only work if you register your details on your pc and tie them in with your ip adress, so the possibility of someone fitting all those criteria are there but the chances are slim, however just because that small possibility exists there is no need to assume that "privacy is obsolite" it is an obviosly silly idea to give out your personals on that preconception!